As is known, conveyor belts have recently been developed for traveling through an orbit with a generally horizontally extending conveying run overlying a generally horizontally extending return run with the conveying and return run being stretched or elongated to provide a tension in the sides of the conveying run remain in tension as the conveying run traverses a horizontal curve. By retaining the sides of the conveying run in tension as the conveying run traverses a horizontal curve the material being transported is maintained on the conveying run rather than permitting excess spillage as occurs with prior, non-special forms of conveyor belts. The original description of such a tensioned conveyor belt is set forth in U.S. patent application Ser. No. 06/069,664, now abandoned, and U.S. Pat. No. 4,387,801, wherein one embodiment of a conveyor belt is disclosed and described having a selected limited elongation for establishing the overall length of an orbital conveyor belt. Such conveyor belt elongation is obtained by fastening an orbital drive chain to the resilient conveyor belt with the belt in its relaxed or slack condition, i.e., without any longitudinal tension being applied to the belt runs, with a specific spatial relationship between adjacent links of the chain. When such chain is longitudinally tensioned, as is the case when supported for travel through an orbital path as shown in U.S. Pat. No. 4,339,031, the slack between adjacent links of the chain is eliminated or taken up and the chain becomes taut. The slack eliminating tensioning of the chain also simultaneously elongates the conveyor belt to the same linear extent as the chain is elongated when moving from a slack to taut position. Thus, a preselected elongation is achieved in the conveyor belt as determined by the total slack between adjacent links of the chain. A similar functioning slack-taut chain is also disclosed in the patent application Ser. Nos. 116,722, now abandoned, and 346,683, the continuation application thereof; however, the chain of such applications comprises links which are identical in form. As can be readily appreciated, the providing of formed chain links to drive a conveyor belt represents a considerable expense and the operation of a metallic chain over metallic drive and/or idler sprockets creates a level of noise which may be objectionable. Preferably drive chain noise is maintained at an acceptable level.
Other prior conveyor belts have been designed to traverse horizontal curves such as a special form of conveyor belt as shown in U.S. Pat. Nos. 3,545,598 and 3,701,411. Such belts incorporate molded edge flutes which fold and unfold as required in traversing a horizontal turn. Such molded flute structure is expensive and subject to possible excessive wear due to the accumulation of particles of the material being conveyed in the flutes which may abrade the flutes as they fold and unfold. Another prior conveyor belt structure, shown in U.S. Pat. No. 4,061,223, requires a separate belt driving element, disclosed as a drive or power belt, which contacts the conveying belt to drive the conveying belt. As the power belt stretches an indeterminate amount, it is not possible to apply a driving force to the power belt without stretching the power belt. Such stretching of the power belt varies and is uncontrollable so that the power belt cannot be driven by conventional belt drives or installed on conventional conveyor belt supports.